In the present industrial society, many high buildings have been constructed. In case of a fire taking place in the high building, people in a building would usually have difficulty in escaping down an extension type ladder because the height of the ladder is limited. As result, some of the escapees would jump from the building to cause injuries or casualties. Some buildings have been provided with rope type escape devices wherein rope clamp devices are attached to a person to control the rate of descent along the rope. Most of the conventional escape devices comprises mainly two clamping blocks to hold a rope therebetween; when the grips on the blocks are pushed up or down, the two clamping blocks would clamp or release the rope. Such a clamping device has the drawback of causing the rope to slide, and the space between the two clamping blocks usually does not adapt to the diameters of some ropes; therefore, the aforesaid drawbacks in operation should be eliminated as much as possible.